Runoff Quality from Roofing during Early Life

Sustainable water management involves ensuring that site runoff not exceed the pre-development peak flow rate and volume, typically accomplished through the use of water retention, infiltration, and reuse onsite. One example is rain harvesting from roofs. However, certain roofing materials can be a pollutant source in urban runoff, thus, influencing the runoff pollution potential. This project focuses on the first four months of roof life for specific traditional roofs and an extensive green roof. Substantial and significant releases of zinc and copper are found to originate from an uncoated galvanized roof and from two treated woods, respectively. Roof runoff concentrations during early life indicate potential toxicity concerns for zinc and copper, plus periodic elevated nutrient concentrations. Additionally, periodic spikes in pollutant concentrations throughout this early life indicates that elevated pollutant levels simply are not a result of washoff from excess preservative remaining on the surface of the material at installation.